This invention relates to a valve seal, and more particularly to a bidirectional valve seal in which pressure in the fluid line makes sealing more effective.
The prior art shows many types of seals for butterfly valves. Perhaps the simplest seal uses a solid resilient member. In one form, the resilient member is captured in the valve body and has an annular surface that seals against the valve disc. U.S. Pat. Nos. 3,591,133 to Miles et al; 3,608,861 to Helman et al; 3,997,142 to Broadway; 4,114,856 to MacAfee et al; and 4,210,313 to Chester; and British Pat. No. 1,203,029 to Jarrett show such sealing arrangements. A variation of that approach mounts the solid resilient member to the disc and an annular surface on the resilient member seals against the valve body. U.S. Pat. Nos. 3,658,292 to Takigawa and 4,154,426 to Santy et al disclose duch seals.
Another seal uses a sealing member similar to those discussed above, except that the member has an annular cavity rather than being solid. Within the annular cavity is another separate resilient member. The outer member may be of a material relatively impervious to the media carried through the valve and the inner member provides the resistance to deformation that optimizes sealing. U.S. Pat. No. 3,563,510 to Priese shows that type of seal, in which a rubber or elastomeric O-ring or a helically wound, round-wire spring, comprises the inner member. Another variation of that approach uses a flat-wire spring as the resilient inner member held between two legs of the outer member clamped in the valve body. The two legs of the outer member have a spacing member between them that provides a bearing surface to resist radially outward movement of the inner member when the disc closes. That type of seal is incorporated in valves sold by the Duriron Company, Inc. of Cookeville, Tenn. under the name "Big Max".
A third type of seal uses a sealing member that "floats" in a cavity in the valve body and has a backing member in the cavity to urge the floating member radially inwardly against the valve disc. U.S. Pat. Nos. 3,282,558 to Swain; 3,497,178 to Priese; 3,642,248 to Benware; 3,986,699 to Wucik, Jr. et al; 4,088,299 to Maciulaitis et al; 4,113,268 to Simmons et al; 4,130,285 to Whittaker; 4,165,859 to Maciulaitis et al; and 4,194,749 to Bonafous disclose seals that use that approach. Those patents disclose various devices as the backing member. For example, in one embodiment of Benware's seal, an O-ring deforms in cross-section when system pressure enters the cavity and wedges against the sealing member to urge it radially inwardly against the valve disc. It is known that the seal shown in Benware has also used a flat-wire spring backing member. The flat-wire spring provides resistance to the radially outward urging of the floating member by reacting against the bottom of the cavity, thus holding the floating member against the disc. The seal shown in the Bonafous patent functions in a similar manner, but uses a round-wire instead of a flat-wire spring. The Benware patent, and other of those patents such as the Whittaker patent, also show a garter spring as the backing member. The garter spring creates hoop compression in the sealing member to urge it against the valve disc and thus generally creates a sealing action different from that created by a backing member that is resilient in cross-section.
A final type of seal uses a sealing member having one leg held in the valve body. The sealing member and the valve body define a cavity. Generally, although not always, the cavity has a backing member in it. U.S. Pat. Nos. 2,988,320 to Kent; 3,260,496 to Borcherdt; 3,734,457 to Roos; 4,005,848 to Eggleston; and 4,044,994 to Priese, and the "Series 206 Valves" made by Royal Industries of Santa Ana, Calif., show embodiments of that approach. The Kent U.S. Pat. No. 2,988,320 and Priese U.S. Pat. No. 4,044,994 patents show a round-wire garter spring that creates hoop compression in the disc to urge the sealing member radially inwardly. The Roos patent uses flat metal hoops for the same purpose. The Eggleston patent uses a round-wire garter spring in the cavity as a fulcrum about which the sealing member can bend under system pressure. In that way, the sealing member is urged against the valve disc.
The typical structure for holding annular seals, like those used for butterfly valves, in place includes a retaining ring held against a valve body. The seal is disposed in an annular slot formed by the valve body and retaining ring. The valve body includes flanges for connecting the valve to flanges on the fluid line.
In the prior art, the retaining ring is held against the valve body by bolts disposed axially through the valve body and retaining ring. An example of such an arrangement is shown in the Broadway patent. With that configuration, the heads of the bolts must be recessed into the axial face of the retaining ring because the flanges on the fluid line bear directly against the axial face of the retaining ring.